Enumerate through geometry objects in scene
You can check for an objects 'type':

for ob in context.scene.objects:
    if ob.type == 'MESH':
        print ob


Other 'types' include:

CURVE, SURFACE, META, FONT, ARMATURE, LATTICE, EMPTY, CAMERA, LAMP, SPEAKER.

If you want to check for multiple types you can used Python's set notion.

for ob in context.scene.objects:
    if ob.type in {'MESH', 'CURVE', 'SURFACE'}:
        print ob